Not to be a complete poindexter but...
There's a lot of conflation between entity types (for purposes of registration from the state) and taxation structures. It's also frustrating that many of the names are quite similar.
An LLC is a limited liability company, which is one of the many types of entities you can choose to create under Iowa law.
The most common types of entities are LLCs, corporations, and partnerships. Keep in mind that there are a ton of different types of partnerships (limited partnerships, limited liability partnerships, limited liability limited partnerships, general partnerships), and many doctors/lawyers use what's called a "professional corporation." However, again, these all generally fall under those three types.
Your type of entity is what decides how the entity actually functions, your registration with the state, and some of the administrative options that you have.
C-corp, S-corp, and partnerships are the three most common taxation statuses for entities (this ignores the various types of nonprofits and other non-taxable entities....). Confusingly, "partnership" is both an entity type, as well as one of the big tax elections.
C-corp taxation status is generally a good choice if you anticipate the business becoming publicly traded down the line. C-corps get taxed at the corporation level, AND at the distribution level. This is often referred to as the "double tax." Smaller businesses would almost never want to choose a C-corp tax election.
Partnerships are "pass-through" entities, where the income of the business is "passed through" to the individual owners and their proportional share of the profits is treated like income for the individual. This avoids the "double tax" issue, but it's also a lot more complicated from a tax administration perspective... Of course, there are probably hundreds of law firms, CPAs, and other tax professionals who are happy to help you out to make it a lot simpler for the user.
S-corp status used to be incredibly popular, and still is to some extent, for smaller businesses. S-corps are a bit of a hybrid between C-corps and partnerships from a tax perspective. It's generally a pass-through entity, but also gets a few benefits with favorable treatments for self-employment taxes.
Corporations (the business type) are by default taxed as a c-corp, but can file an s-corp election. Partnerships are by default taxed as a partnership. LLCs by default are also taxed as a partnership, but can make an s-corp election. In general, LLCs are typically the most flexible entities from a tax perspective, and they also have some administrative benefits (the code for LLCs requires a bit less when it comes to maintenance/upkeep than the code for corporations).
Most small businesses will form as an LLC, and then either choose to be taxed as a partnership or as an s-corp. Consult a tax professional and a lawyer (and sometimes these are the same person). It all depends on what the assets are, how many members there are, what the goals of the entity are, and other factors that require a LOT more in depth information than what's good to post on a public board.
